High-efficiency perovskite solar cells based on anatase TiO2 nanotube arrays

• 1D anatase TiO2 nanotubes were used to fabricate perovskite solar cells.
• The best efficiency of 11.3% was achieved with ~ 0.40 μm-long TiO2 nanotubes.
• The efficiency of the devices decreased with increasing TiO2 nanotube lengths.

Perovskite solar cells (PSCs) based on one-dimensional anatase TiO2 nanotube arrays were prepared by using a two-step deposition method to fill the arrays of TiO2 nanotubes in different lengths with perovskite. The photovoltaic performance of PSCs was found to be significantly dependent on the length of the TiO2 nanotubes, and the power conversion efficiency decreased as the length of the TiO2 nanotubes increased from ~ 0.40 μm to ~ 0.65 and then to ~ 0.93 μm. The PSC fabricated with ~ 0.40 μm-long anatase TiO2 nanotube arrays yielded a power conversion efficiency of 11.3% and a fill factor of 0.68 under illumination of 100 mW/cm2 AM 1.5G simulated sunlight, which is significantly higher than previously reported solar cells based on 1-D TiO2 nanostructures. Incident photon-to-current efficiency and electrochemical impedance spectroscopy measurements indicated that longer TiO2 nanotubes led to higher recombination losses of charge carriers, possibly due to poor filling of the nanotube arrays with perovskite.